Sheet separator in a loading system and method for separating sheets during loading

ABSTRACT

According to some embodiments of the invention, a method for separating sheets is provided. The method comprises positioning onto a stack of sheets grippers having suction cups attached to vertical rods, then applying vacuum to the suction cups, and while maintaining the vacuum, raising the rods to lift one or more of sheets and then vertically moving the rods up and down according to a predefined motion scheme.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority from U.S. provisional application Serial No. 60/301,815, filed Jul. 2, 2001.

BACKGROUND OF THE INVENTION

[0002] Loading devices are commonly used to handle sheets of rigid or semi-rigid material such as cardboard during various processing operations such as industrial packaging printing. Commonly, cardboard sheets are supplied by the manufacturer in stacks. In many manufacturing processes, sheets may be loaded, one by one, from the top of the stack by a loader. The sheet may then be moved into a processing unit, such as, for example, a printing system. After completing the processing operation, a delivery system may remove the processed sheet to another stack or to another processing unit.

[0003] Electrostatic charges, vacuum forces, and residual adhesive substances may cause sheets to cling together such that a conventional loader may lift more than one sheet at a time. Whenever two or more sheets are accidentally loaded together, human intervention may be needed in order to separate them causing a decline in manufacturing throughput.

BRIEF DESCRIPTION OF THE DRAWINGS

[0004] The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings in which:

[0005]FIG. 1 is a schematic illustration of a loader according to some embodiments of the present invention;

[0006]FIG. 2 is a schematic illustration of a gripper and a vertical motion unit according to some embodiments of the present invention;

[0007]FIG. 3 is a schematic illustration of a loader according to some embodiments of the present invention;

[0008]FIG. 4 is a schematic illustration of a gripper coupled to a vacuum pump according to some embodiments of the present invention;

[0009]FIG. 5 is a flow chart illustration of a sheet separation method according to some embodiments of the present invention;

[0010]FIGS. 6A and 6B are exemplary schematic representations of a sheet separation method according to some embodiments of the present invention;

[0011]FIGS. 7A and 7B are exemplary schematic representations of another sheet separation method according to some embodiments of the present invention; and

[0012]FIGS. 8A and 8B are exemplary schematic representations of another sheet separation method according to some embodiments of the present invention.

[0013] It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0014] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, components and circuits have not been described in detail so as not to obscure the present invention.

[0015] Some embodiments of the present invention are directed to a method and apparatus for separating sheets of rigid or semi-rigid material during a loading process such that only one sheet may be loaded onto a loading plane at a time. Non-limiting examples of rigid or semi-rigid sheets suitable for some embodiments of the present invention may be cardboard, paper, metal and plastic.

[0016] Reference is now made to FIG. 1, which is a schematic illustration of a loader according to some embodiments of the present invention. Loader 10 may comprise a transport mechanism, generally designated 12, and a gripping mechanism 14 coupled to the transport mechanism. Gripping mechanism 14 may grip a sheet 15 from the top of a stack of sheets 16 and then transport mechanism 12 may move sheet 15 onto a loading plane (not shown) for further processing. In the descriptions and the claims that follows the term horizontal refers to being parallel to the stack of sheets and the term vertical refers to being perpendicular to the stack of sheets.

[0017] Transport mechanism 12 may comprise one or more rails 18 positioned above and substantially parallel to stack 16 and a motorized carriage 20 movable along rails 18. Carriage 20 may comprise two or more bars 22 positioned perpendicular to rails 18. Gripping mechanism 14 may comprise two or more arrays of grippers 24, each array attached to one of bars 22. Gripping mechanism may further comprise two or more vertical-motion units 26, each attached to one of bars 22. Loader 10 may further comprise a vacuum pump 28 coupled to grippers 24 and an energy source 29 coupled to motion units 26. Loader 10 may further comprise a controller 30 coupled to vacuum pump 28 and to energy source 29.

[0018] Energy source 29 may be able to supply energy to enable vertical movement within motion unit 26. Non-limiting examples of such an energy source may be a an air pressure unit, an electromechanical device, a hydraulic device and a pneumatic device and any other device capable of generating a vertical movement. FIG. 2 illustrates an exemplary embodiment for which a vacuum lift force is used. In this embodiment, motion units 26 may be coupled to vacuum pump 28 and to an air pressure unit 31.

[0019] Reference is now made to FIG. 2, which is a schematic illustration of a gripper and a vertical motion unit according to some embodiments of the present invention. Gripper 24 may comprise a vertical rod 32 and a suction cup 34 coupled to rod 32. Gripper 24 may further comprise a spring 36 within rod 32 to enable good contact with the top surface of the sheet, which may not be totally flat. Rod 32 may be coupled to a vacuum pump 28 via a pipe 38 and a valve 40. Valve 40 may be coupled to controller 30, which may activate valve 40 when needed.

[0020] Vertical-motion unit 26 may comprise a tube 42 and a rod 44 and may be coupled to air pressure unit 31 via pipes 46A and 46B and a valve 48. Alternatively, vertical-motion unit 26 may be coupled to another energy source. In other embodiments, which will be described with respect to FIGS. 3 and 4, unit 26 and gripper 24 may be integrated into a single unit.

[0021] Reference is now made to FIG. 3, which is a schematic illustration of a loader according to some embodiments of the present invention and to FIG. 4, which is a schematic illustration of a gripper according to some embodiments of the present invention. Loader 50 may comprise a transport mechanism, generally designated 52, and a gripping mechanism 54 coupled to the transport mechanism. Gripping mechanism 54 may grip a sheet 15 from the top of a stack of sheets 16 and then transport mechanism 52 may move sheet 15 onto a loading plane (not shown), [such as a printing table] for further processing.

[0022] Transport mechanism 52 may comprise one more arms 56 positioned above and substantially parallel to stack 16, each arm movable within a corresponding support tube 58. Gripping mechanism 54 may comprise one or more arrays of two or more grippers 60, each array attached to a corresponding arm 56. For purpose of illustration, four grippers, labeled 60A, 60B, 60C and 60D are shown. However, the invention is not limited to this configuration only. As can be best seen in FIG. 4, gripper 60 may comprise a tube 62, a piston-type rod 64 able to move inside tube 62, and a suction cup 66 attached to rod 64. Suction cup 66 may be coupled to vacuum pump 28 via a pipe 68 and a valve 70. Controller 30 may activate valve 70 to apply vacuum to suction cups 66. Tube 62 may be coupled to vacuum pump 28 and to air pressure unit 31 via a pipe 72 and a valve 74. Controller 30 may activate valve 74 to apply alternately vacuum and pressure to tube 62, thus causing rod 64 to move up and down within tube 62.

[0023] Reference is now made to FIG. 5, which is a flowchart diagram of a method for separating sheets according to some embodiments of the present invention. First suction cups may be brought into contact with the top surface of a top sheet of stack 16 (block 500) A vacuum force may then be applied substantially simultaneously to suction cups 64 (block 502). The loader may then be moved upward while lifting one or more sheets (block 504). Then, controller 30 may activate energy source 29, such as air pressure 31 to move vertically piston-type rod 64 or motion unit 26 according to a predefined scheme (block 506). The predefined scheme may determine the amplitude, frequency and duration of up and down rapid movements. The sheets gripped by suction cups 64 are moved accordingly.

[0024] Rod 44 or 64 may be rapidly moved up and down within tube 42 or 62. When vacuum pump 28 and/or air-pressure unit 31 is the energy source for the vertical movement, alternate pressure and vacuum may be appled to rods 44 or 64. The rapid movement may cause sheets that may stick to the top sheet to fall back onto stack 16 (block 508). When movement is stopped, the transport mechanism may move a single sheet to a loading plane (block 510).

[0025] The method described hereinabove may be useful to overcome vacuum or electrostatic forces causing the sheets to stick together. The rapid movements may create a force that is stronger than the sticking force but weaker than the suction force. Therefore, the lower sheets may separate from the upper sheet, which is held by the suction force. The amplitude, frequency and duration of the rapid movements may be determined according to the material and the rigidity of the sheets.

[0026] The following examples are given now, though by way of illustration only, to show certain schemes of vertical movements according to some embodiments of the present invention without limiting its scope. In these examples, for purposes of clarity, only two grippers are shown. Furthermore, only two sheets are shown lifted by the suction cups, however it should be noted that more than two sheets may be lifted by the suction cups and that probably in many cases only one sheet is lifted.

[0027] Reference is now made to FIGS. 6A and 6B, which schematically illustrate a method for separating sheets according to some embodiments of the present invention. In these embodiments, the grippers may lift sheets 15A and 15B parallel to stack 16 (FIG. 6A). Grippers 80A and 80B may then move simultaneously rapidly up and down in a vertical direction, causing sheet 15A to separate from top sheet 15B and fall back onto stack 16 (FIG. 6B).

[0028] Reference is now made to FIGS. 7A and 7B, which schematically illustrate a method for separating sheets according to some embodiments of the present invention. In these embodiments, sheets 15A and 15B may be lifted to an inclined position above stack 16 such that gripper 80A is closer to stack 16 than gripper 80B. Grippers 80A and 80B may then move rapidly alternately vertically in opposite directions. For example, as shown in FIG. 7B, gripper 80A is moved upward lifting one side of the sheets upward, while gripper 80B is moved downward pushing the other side of the sheets downwards. The rapid alternating movements may induce temporary distortions in the flatness of the top sheet, which may cause the lower sheet 15A to separate from the top sheet 15B.

[0029] Reference is now made to FIGS. 8A and 8B, which schematically illustrate a method for separating sheets according to some embodiments of the present invention. In these embodiments, sheets 15A and 15B may be lifted to an inclined position above stack 16 such that one side of sheet 15A touches stack 16 (FIG. 8A). A downward pressure force may be applied to gripper 80A so that top sheet 15B may be slightly bent, causing sheet 15A to separate from sheet 15B.

[0030] While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those of ordinary skill in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention. 

What is claimed is:
 1. A sheet separator comprising: two or more vertical grippers each having a suction cup; two or more movement units, each of said movement units to move vertically one or more of said grippers independently of at least one other of said grippers; and a controller to activate independently said movement units.
 2. The separator of claim 1, wherein said movement units comprise pneumatic pistons.
 3. The separator of claim 1, wherein said movement units comprise electrical motors.
 4. The separator of claim 1, wherein said movement units comprise mechanical gears.
 5. A sheet separator comprising: two or more grippers comprising longitudinally movable piston rods and suction cups attached to said piston rods; and a controller to instruct an energy source to move one or more of said piston rods independently of at least one other of said piston rods.
 6. The separator of claim 5, wherein said energy source comprises an air pressure unit.
 7. A method comprising: positioning onto a stack of sheets a plurality of suction cups each attached to one of a corresponding plurality of vertical rods; applying vacuum to said suction cups; and while maintaining said vacuum, raising said rods to lift one or more of said sheets and then vertically moving said rods up and down according to a predefined motion scheme.
 8. The method of claim 7, wherein vertically moving said rods up and down according to said predefined motion scheme comprises vertically moving said rods up and down according to a predefined frequency and amplitude.
 9. The method of claim 7, wherein vertically moving said rods comprises moving said rods substantially simultaneously in the same direction.
 10. The method of claim 7, wherein vertically moving said rods comprises moving at least one of the rods substantially simultaneously in an opposite direction to at least one other of said rods.
 11. A method comprising: positioning onto a stack of sheets a first and a second suction cups of a sheet separator; applying vacuum to said suction cups; while maintaining said vacuum, applying a vertical force on said stack via said first suction cup; and substantially simultaneously, vertically moving upward said second suction cup. 